1. Field of the Invention
This invention relates to sealing means for pressure relief valves and the method of assembly for such sealing means. More particularly, the invention relates to sealing means for a valve member of a pressure relief valve which comprises a valve plate for seating on a valve seat about the inlet of the valve.
2. Description of the Prior Art
Heretofore, such as shown in U.S. Pat. No. 3,722,852 dated Mar. 27, 1973, a pressure relief valve has been provided utilizing a valve plate member mounted on a valve seat about an inlet in fluid communication with a pressure vessel. An outer portion of a flexible membrane in the '852 patent is secured to a large diameter valve plate. An inner portion of the flexible membrane is secured to a retainer plate for the membrane for clamping the membrane between the two plates along a generally transverse axis. A sealing portion of the membrane between the plates is adapted to contact and seal against the valve seat in the closed position of the valve member. Fluid pressure from the dome of the relief valve is exerted against the flexible membrane or diaphragm to urge the membrane into sealing engagement with the valve seat when the valve member is in a closed position. A fluid pressure differential area is provided between opposed faces of the flexible membrane; and the differential pressure either positive or negative urges the membrane into sealing engagement.
At times, particularly when low differential pressures are involved, bubble tight sealing will not be provided by the flexible membrane as shown in U.S. Pat. No. 3,722,852 as pressure is required to energize the seal. Increased environmental standards require substantially bubble-tight sealing at very low differential pressure or at zero differential pressure exerted against the flexible membrane or diaphragm.